Background: Approximately 56% of people with multiple sclerosis (pwMS) will fall in any three-month period with the potential for physical, psychological and social consequences. Falls prevention research for pwMS is in its infancy with a timely need to develop theory-based interventions that reflect the complexity of falls. The clear articulation of the development of any complex intervention is paramount to its future evaluation, usability and effectiveness. Methods: This paper aims to describe how the development of “Better Balance,” a complex multicomponent falls prevention intervention for pwMS, was guided by the Medical Research Council framework for the development of complex interventions. Sources of information included existing literature, original research, clinician interviews and views of pwMS. These sources were synthesized and refined through an iterative process of intervention development involving researchers, clinicians and pwMS. Results: The resulting intervention is outlined through a number of key tasks supplementing the original Medical Research Council framework. The utilization of this framework resulted in a theoretically-based and user-informed complex intervention designed to address the physiological, personal and behavioral risk factors associated with falls in pwMS. Conclusions: The articulation of the systematic process used to develop Better Balance will inform the future evaluation and usability of the intervention.